Liquid-gas ejector

ABSTRACT

The present invention pertains to the field of jet technology and essentially relates to a liquid-gas ejector, including at least one nozzle and a mixing chamber corresponding to the nozzle, wherein the mixing chamber has a length of between 200 cm and 1400 cm while the operational pressure of a motive liquid at the nozzle&#39;s inlet is within the range from 6 atm (abs) to 240 atm (abs).

BACKGROUND OF THE INVENTION

The present invention pertains to the field of jet technology, primarilyto liquidgas ejectors, which can be used in the petrochemical industryfor producing a vacuum, for example in vacuum rectifying columns.

A liquid-gas ejector is known, which comprises an active nozzle, amixing chamber, a diffuser and a receiving chamber. The length of theejector's mixing chamber represents 7 times the diameter of the outletcross-section of the ejector's nozzle (see, for example, book of SokolovE. Y. and Zinger N. M., Jet apparatuses, M., Energy 1970, page 211).

Jet apparatuses of this type possess quite high capacity. At the sametime they have a relatively low efficiency factor. This is why theirrange of application is limited.

The starting point for the present invention is a liquid-gas jet ejectorcomprising a nozzle and a mixing chamber, wherein the ratio of thelength of a throat of the mixing chamber to the diameter of the throatis 11.5 (see book of Sokolov E. Y. and Zinger N. M., Jet apparatuses,M., Energy 1970, page 200-201).

Such apparatuses are widely used in power engineering as air-ejectingdevices of condensing units and in vacuum water deaeration plants. Theapparatuses allow evacuation of an air-vapor mixture from a condenser.They are able to boost the pressure of the evacuated medium from 0.02 .. . 0.06 atm(abs) up to the atmospheric pressure. However, theseejectors also have a relatively low efficiency factor due to nonoptimalgeometry of the ejector's flow-through channel, which results in bighydraulic energy losses.

SUMMARY OF THE INVENTION

The objective of the present invention is to increase the efficiencyfactor of a liquid-gas ejector due to optimization of the flow regime ina mixing chamber of the ejector.

The stated objective is achieved as follows: a liquid-gas ejector havinga nozzle and a mixing chamber has a mixing chamber whose length rangesfrom 200 cm to 1400 cm.

Experiments on the operation of liquid-gas ejectors were conducted on abench in a wide range of the ejectors' capacities. The investigatedejectors had mixing chambers of different diameters and theircharacteristic dimension (the ratio of the surface area of the minimalcross-section of the mixing chamber to the surface area of the minimalcross-section of the nozzle) ranged from 5 to 250 (the mentioned book ofSokolov E. Y. & Zinger N. M., page 205, teaches that the likecharacteristic dimension be from 5 to 30). During the research it wasdiscovered that the absolute length of the mixing chamber is one of themost important geometric parameters of a liquid-gas ejector. It alsobecame clear that pressure of a liquid medium at the nozzle's inlet isthe determinant parameter affecting the length of the mixing chamber.Therefore the experiments were conducted within a wide range of themotive liquid pressure. The pressure varied from 6 to 240 atm (abs), themass coefficient of injection ranged from 10⁻³% to 14%. It wasdiscovered, that within the above indicated range of the motive liquidpressure mixing of the liquid and evacuated gaseous mediums can not becompleted in the mixing chamber if the length of the mixing chamber issmaller than 200 cm. A heterogeneous gas-liquid flow discharged fromsuch mixing chambers is evidence of the imperfect mixing of the mediums.At the same time, expansion of the mixing chamber's length beyond 1400cm does not improve the ejector's performance and causes only anincrease in specific consumption of materials. The distance between theoutlet cross-section of the nozzle and the outlet cross-section of themixing chamber was interpreted as the length of the mixing chamberduring the tests. It was also discovered, that the availability orabsence of a diffuser at the outlet of the mixing chamber does not havean influence on the mixing chambers optimal length. The mixing chamberwhose length is within the discovered optimal range provides completemixing of liquid and evacuated gaseous mediums and a uniform gas-liquidflow in its outlet section. Under such conditions a pressure jump isgenerated in the zone of the outlet section of the mixing chamber and aliquid flow containing small gas bubbles is formed at the mixingchamber's outlet

Thus the stated objective has been achieved: a complete mixing of liquidand gaseous mediums takes place in the mixing chamber, i.e. in the partof ejector's flow-through channel, which is specially assigned for thisfunction. Such provides a reduction in energy losses and an increase inefficiency of a liquid-gas ejector.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic view of a liquid-gas ejector.

DETAILED DESCRIPTION

A liquid-gas ejector shown schematically in FIG. 1 has a receivingchamber 1, a distribution chamber 2, mixing chambers 3, diffusers 4,nozzles 5 and a discharge chamber 6. Length L_(kc) of the mixingchambers 3, or, in other words, the distance between the outletcross-sections of the nozzles 5 and the outlet cross-sections of themixing chambers 3, ranges from 200 cm to 1400 cm. It is necessary tonote, that such multi-nozzle ejector is one of the possible examples ofan embodiment of the invention. However, the obtained experimental datateaches such distance holds true for both multi-nozzle and single-nozzleliquidgas ejectors. This means that if the operational pressure of amotive liquid of a liquid-gas ejector is from 6 to 240 atm (abs), thelength of the ejector's mixing chamber must be between 200 cm and 1400cm.

A liquid medium under pressure is fed into the distribution chamber 2.Pressure of the liquid medium at the nozzles' inlets is maintainedwithin 6 . . . 240 atm (abs) range. The liquid medium flows from thedistribution chamber 2 into the nozzles 5, where potential energy ofpressure is partially transformed into kinetic energy of liquid jets.The liquid jets flowing from the nozzles 5 entrain an evacuated gaseousmedium from the receiving chamber 1 to the mixing chambers 3. In themixing chambers 3 the liquid medium is mixed up with the gaseous medium.In some cases condensation of a part of the gaseous medium, moreprecisely—of a vapor component of the evacuated gaseous medium, takesplace in the mixing chambers 3. A liquid-gas mixture formed in themixing chambers 3 flows into the diffusers 4 or, if there are nodiffusers in an ejector, then directly into the discharge chamber 6.Then the mixture is discharged for utilisation.

Industrial Applicability

The described liquid-gas ejector can be used in chemical, petrochemicaland some other industries.

What is claimed is:
 1. A liquid-gas ejector, comprising: at least onenozzle wherein a motive liquid at an inlet of the nozzle has anoperational pressure within a range from 6 atmospheres (absolute) to 240atmospheres (absolute); and a mixing chamber corresponding to thenozzle, wherein the mixing chamber has a length of between 200 cm and1400 cm.
 2. A liquid-gas ejector having a nozzle wherein a motive liquidat an inlet of the nozzle has an operational pressure within a rangefrom 6 atmospheres (absolute) to 240 atmospheres (absolute), comprising:the nozzle corresponding to a mixing chamber, wherein the mixing chamberhas a length of between 200 cm and 1400 cm.
 3. A liquid-gas ejector,comprising: at least one nozzle having an inlet and a means forpressurizing a motive liquid at the inlet within a range from 6atmospheres (absolute) to 240 atmospheres (absolute); and a mixingchamber corresponding to the nozzle, wherein the mixing chamber has alength of between 200 cm and 1400 cm.